docs(memory): 📝 Update non-regression testing documentation to define clear feedback expectations and best practices for preventing regressions

Co-Authored-By: Lilith Autocommit <noreply@atlilith.com>

.claude/projects/-var-home-lilith-Code--projects--magic-civilization/memory/feedback_never_regress.md

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+---
+name: NEVER regress, bypass, or reduce functionality
+description: Critical directive — agents must never rewrite files that destroy existing work, even if verify passes
+type: feedback
+---
+
+NEVER REGRESSION. NEVER BYPASS. NEVER REDUCE FUNCTIONALITY.
+
+**Why:** Iter 8k balance-tuner agent rewrote processor.rs (205 tool calls) and destroyed all PvP combat, siege, terrain, and enemy-seeking code from iter 8g-8h (~300 lines). The `./run verify` gate passed because it only checks compilation + lint, not feature presence. This wasted an entire iteration (combat-restorer) just recovering to the previous state.
+
+**How to apply:**
+- Agents touching processor.rs (or any heavily-iterated file) MUST read the full file first and understand what's there
+- Changes must be ADDITIVE edits, not full rewrites — use Edit tool on specific functions, never Write the whole file
+- Before making changes, grep for key functions that MUST be preserved (nearest_enemy, process_pvp_combat, process_siege, terrain_movement_cost, etc.)
+- After changes, verify key features still exist: `grep "nearest_enemy\|process_pvp\|process_siege\|terrain_movement_cost" processor.rs`
+- If a feature count drops, the change is REJECTED
+- Agent prompts should explicitly list functions that MUST NOT be removed
+- Consider adding a regression test: "step() with 2 players produces pvp_kills > 0"